The present invention relates to an optical system for illuminating and viewing a target.
An optical system for illuminating and viewing a target, which comprises a target, a source of illumination of the target and means for receiving the light remitted from the target, can be defined by an illumination axis and optical axis that converge at the target
Such an optical system may be as simple as an operator of an illumination source viewing a target, wherein the operator embodies the means for receiving the light remitted from the target. An example of such an optical system is an operator of a vehicle, that is inside the vehicle and is looking out at an illuminated target such as a road or tunnel walls.
More complex optical systems include automated processors as means for receiving the light remitted from a viewed target. Examples of such optical systems can be found in diagnostic apparatuses such as endoscope devices. The endoscopes described in the art comprise an image pickup element and an illuminating element for illuminating an examined target.
For these optical systems it is advantageous to have the illuminating element and receiving means contained within a single compartment, namely behind a single optical window.
In a vehicle carrying an operator, the illuminating elements are usually situated outside the vehicle, thereby requiring the operator to leave the vehicle for repairs or the like. In vehicles such as submarines or trains traveling in a dark tunnel, this may be a perilous task.
In diagnostic apparatuses, especially those meant to be inserted into body orifices, having a single optical window is advisable for hygienic and practical considerations.
A frequent problem encountered in having the illumination element and means for receiving remitted light contained behind a single optical window is the xe2x80x9cnoisexe2x80x9d (backscatter and stray light) produced by light remitted from the optical window itself, which is received by the receiving means.
Presently used techniques for reducing noise include utilizing light guiding means, or separating the illumination element from the receiving means.
For example, U.S. Pat. No. 5,840,014 (Miyano et al.) describes an endoscope having an illumination window and a viewing window having a detachable protective covering and a transparent material for purging air from the space between the front end and the detachable covering, for lowering loss in illumination light quantity.
The present invention provides an optical system for illuminating and viewing a target in which an illumination element and a receiving means are disposed behind a single optical window, and which obtains data essentially free of backscatter and stray light.
The optical system according to the present invention comprises at least one illumination element and at least one receiving means, both disposed behind a single optical window having a plurality of reflecting surfaces.
The optical window is configured such that it defines a shape having at least one focal curve.
At least one illumination element and at least one receiving means are geometrically positioned on the focal curve plane or in proximity of the focal curve plane, such that, when illuminating, rays from the illumination elements, that are internally reflected from the optical window surfaces, will not be incident on the is receiving means.
It will be appreciated that the term xe2x80x9creceiving meansxe2x80x9d relates to any means suitable for receiving, processing or further transmitting illumination rays remitted from a target or data derived from these rays.
In an embodiment of the invention the optical window is an ellipsoid shaped dome. A plurality of illumination elements are positioned on the ellipsoid focal curve and a receiving means is positioned on the axis of symmetry of the ellipsoid at an equal distance from the illumination elements.
The components of the system, thus positioned, ensure that when illuminating, all the light internally reflected from the optical window surfaces is received at points on the focal curve and is not incident on the receiving means.
The present invention further provides a diagnostic instrument comprising an optical system according to the present invention.